Acetylene Lewis structure

Multiple bonds are very common m organic chemistry Ethylene (C2H4) contains a carbon-carbon double bond m its most stable Lewis structure and each carbon has a completed octet The most stable Lewis structure for acetylene (C2H2) contains a carbon-carbon triple bond Here again the octet rule is satisfied... 

Now consider the alkynes, hydrocarbons with carbon-carbon triple bonds. The Lewis structure of the linear molecule ethyne (acetylene) is H—O C- H. To describe the bonding in a linear molecule, we need a hybridization scheme that produces two equivalent orbitals at 180° from each other this is sp hybridization. Each C atom has one electron in each of its two sp hybrid orbitals and one electron in each of its two perpendicular unhybridized 2p-orbitals (43). The electrons in the sp hybrid orbitals on the two carbon atoms pair and form a carbon—carbon tr-bond. The electrons in the remaining sp hybrid orbitals pair with hydrogen Ls-elec-trons to form two carbon—hydrogen o-bonds. The electrons in the two perpendicular sets of 2/z-orbitals pair with a side-by-side overlap, forming two ir-honds at 90° to each other. As in the N2 molecule, the electron density in the o-bonds forms a cylinder about the C—C bond axis. The resulting bonding pattern is shown in Fig. 3.23. 

Acetylene (ethyne), C2H2, can be polymerized, (a) Draw the Lewis structure for acetylene and draw a Lewis structure for the polymer that results when acetylene is polymerized. The polymer has formula (CH), where n is large, (b) Consider the polymers polyacetylene and polyethylene. The latter has the formula (CH2)W and is an insulating material (plastic wrap is made of polyethylene), whereas polyacetylene is a darkly colored material that can conduct electricity when properly treated. On the basis of your answer to part (a), suggest an explanation for the difference in the two polymers. 

C09-0016. Determine Lewis structures for the following molecules (a) H2 NCH2 CH2 NH2 (b) HCCH (acetylene, used in welding torches) and (c) (H3 C)2 CO (acetone, an organic solvent). 

Many of the Lewis structures in Chapter 9 and elsewhere in this book represent molecules that contain double bonds and triple bonds. From simple molecules such as ethylene and acetylene to complex biochemical compounds such as chlorophyll and plastoquinone, multiple bonds are abundant in chemistry. Double bonds and triple bonds can be described by extending the orbital overlap model of bonding. We begin with ethylene, a simple hydrocarbon with the formula C2 H4. 

The Lewis structure of acetylene (C2 H2) shows a triple bond between the carbon atoms ... 

Sigma and pi NBOs of hydrocarbons ethane, ethylene, acetylene Let us turn now to the actual NBOs for the classical cases of equivalent sp" hybridization acetylene (n = 1), ethylene (n = 2), and methane (n = 3). In each case, the NBO results are in excellent agreement with the expected Lewis structures,... 

The leading NBO Lewis structure of the less strongly bound Au(HCCH)+ complex does indeed correspond to separated Au+ HCCH reactants. Figure 4.89 illustrates the principal NBO donor-acceptor interactions for the Au(HC=CH)+ complex, which are seen to be rather similar to those for the long-range Ti(H2C=CH2) complex (Fig. 4.72). Thus, for a transition metal with only one vacant valence orbital, acetylene and ethylene 7tCc bonds function rather similarly as two-electron donors, and the p2, two-electron complex description is apt. 

A simple compound with a triple bond is ethyne (acetylene), HC=CH. The Lewis structure for ethyne is shown in Figure 3.14a. It is a linear molecule. One of the CC bonds is a sigma bond. The other two are pi bonds. 

In Section 2-4, we studied the electronic structure of a triple bond. Let s review this structure, using acetylene as the example. The Lewis structure of acetylene shows three pairs of electrons in the region between the carbon nuclei ... 

Acetylene (C2H2) has a triple bond. Its Lewis structure shows three pairs of electrons between the carbon atoms to give them octets. The following examples show organic compounds with triple bonds. A triple dash (=) symbolizes a triple bond. 

This uses all 10 electrons each C has an octet, and each H has two electrons. The Lewis structure is valid. Acetylene contains a carbon-carbon triple bond. 

Based on the Lewis structure of acetylene, HC=CH, each carbon atom is singly bonded to one hydrogen atom and triply bonded to the other carbon atom, so each carbon atom is surrounded by two groups. As a result ... 

Another molecule whose bonding can be described by sp hybridization is acetylene (C2FI2), which has the systematic name ethyne. The Lewis structure for acetylene is... 

In still other types of molecules, a central atom is surrounded by only two regions of electron density. Figure 1.10 shows Lewis structures and ball-and-stick models of carbon dioxide (CO2) and acetylene (C2H2). As with double bonds, VSEPR treats triple bonds as one region of electron density. 

Figure 1.22 shows a Lewis structure and an orbital overlap diagram for acetylene, C2H2. A carbon-carbon triple bond consists of one sigma bond and two pi bonds. The sigma bond is formed by the overlap of sp hybrid orbitals. One pi bond is formed by the overlap of a pair of parallel 2p atomic orbitals. The second pi bond is formed by the overlap of a second pair of parallel 2p atomic orbitals. 

Covalent bond formation in acetylene, (a) Lewis structure. 

FIGURE 1.21 Construction of a Lewis structure for ethyne (acetylene). 

PROBLEM 2.42 Write Lewis structures for ethane, ethylene, acetylene, ethanol, ethanethiol, tetraethylammonium ion, diethylphosphine, the imine of diethyl ketone, diethylborane, tetraethylborate ion, diethyl ether, diethyl sulfide, acetaldehyde, acetone, acetic acid, ethyl acetate, acetamide, acetyl chloride, propanenitrile, ethyl fluoride, and ethyl chloride. Show nonbonding electrons as dots and electrons in bonds as lines. 

The concept of valence bond theory and hybridization can also be used to describe the bonding in molecules containing double and triple bonds, such as ethylene (C2H4) and acetylene (C2H2). The Lewis structure of ethylene is... 

The acetylene molecule (C2H2) is linear. Because each carbon atom has two electron domain.s around it in the Lewis structure, the carbon atoms are sp hybridized. As before, promotion of an electron first maximizes the number of unpaired electrons ... 

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